Experimental attempts of sub-micrometer order size machining using micro-EDM

So far, parts larger than several micrometers can be machined by micro-electrical discharge machining (micro-EDM). However, with the growing demands for even smaller parts, sub-micrometer order machining or even nanometer order machining are increasingly required in various industrial areas. In order to meet these requirements, the study on sub-micrometer order manufacturing has become considerably important. In the present study, experimental attempts of sub-micrometer order size machining using micro-EDM was performed, in which the smallest possible size that can be achieved for machined parts was examined, and the factors affecting the manufacturing of sub-micrometer parts were investigated. The results showed that insufficient positioning accuracy, smallest discharge energy and the machined shape error due to the influence of gap control and thermal deformation are not suitable for sub-micrometer machining. Disregarding positioning accuracy and machined shape error, cemented tungsten carbide (WC) and cemented tungsten carbide made of super fine particles (SWC) are relatively better than tungsten (W) from the viewpoint of material structure and influence of residual stress. In particular, SWC is more suitable than WC because both crystal grains size and size of defects among grains are smaller. Setting the polarity of workpiece negative was found to contribute to achieving sub-micrometer machining if the material removal rate is disregarded. Based on these investigation results, sub-micrometer machining using SWC was attempted. The minimum diameter obtained was about 2.8 μm.